Never heard of bookmarkingninja.
Bookmarkwiz does not let you enter in your own URLs. Its made to work seamlessly on the sites it works with (30?) so you get 100% success.
For entering in your own URLs you will need something like bookmarking demon that works off of open source platforms (scuttle, scuttleplus, pligg, phpdug). However it only works when the site admins dont change too much so you will only get it to work with the shit sites. I would imagine that any automated software program that loads up your URLs will have the same problem.